I picked up a copy of SQL Performance Explained last week, after having been a long time fan of Markus’ site Use The Index, Luke!.

What I love the most about use-the-index-luke, is the 3-minute-test. Seriously - try taking it!

Anyway, here is what I have to say about the book:

• Quality : The book is not published by a major publisher, so I was not sure if I should expect a bound stack of photocopies. To my delight, it is the same quality as any other book, and clearly has a copy editor. I didn’t notice any gramatical or copy errors.

• Length : It is a short book at 164 pages + 28 pages of appendixes. I …

The ALTER TABLE statement syntax is explained in the manual at:

http://dev.mysql.com/doc/refman/5.6/en/alter-table.html

To put it simply, there are two ways you can alter the table to use a new character set.

1. ALTER TABLE tablename DEFAULT CHARACTER SET utf8;

This will alter the table to use the new character set as the default, but as a safety mechanism, it will only change the table definition for the default character set. That is, existing character fields will have the old character set per column. For example:

mysql> create table mybig5 (id int not null auto_increment primary key,      
    -> subject varchar(100) ) engine=innodb default charset big5;
Query OK, 0 rows affected (0.81 sec)

mysql> show create table …

Anders posted a blog post about adding a new JSON data type to MariaDB. This made me remember my very first MySQL User conference, well, that and the next couple conferences actually. Why? Because at every conference (for awhile) I remember Brian Aker getting everybody into a room to discuss how to add a data type to MySQL. It was considered pretty much the quintessential example of how to start developing for MySQL because it touches a lot of the basic guts of the server.

The example that Brian always gave was a "hex" data type, so that you can store MD5 numbers using 128 bits of storage instead of 256. A human readable MD5 is a 256 bit string (32 characters) representing 128 bits of actual data. So storing MD5 values in the database (a very common thing) requires twice as much space as it should.

Now, …

I have patched up a MariaDB version with JSON support, just for the fun of it. This is not the best version of MariaDB around, as I am not a MariaDB developer by any means, and although I have played with the MySQL and MariaDB sources before, I have never attemped to look like I know it in detail. So although this works, it's probably full of memory leaks, errors and bad code (my additions, that is).

That said, it actually works. Surprise! For a simple prototype, that is to show off a specific feature.

So, this is what I have: I grabbed MariaDB 10.0.2 sources and worked from there. To support the JSON specifics, I included the Jansson C-library for JSON. So far so good, then I wanted a JSON datatype, that was the first step. Adding a new datatype to MariaDB / MySQL is a pretty major undertaking though, so I decided to try something different, I decided to kidnap …

I had to type in the location and name of my identity file and a long string of username@hostname anytime I'd try to SSH into my Amazon EC2 instance for administration. I found an easy solution that I am sharing with you here.

Here is a fix for the MySQL/TokuDB/MariaDB bug I reported earlier today.  I think this fix is correct (it is only one line) but I don’t delve into the storage engine very often (and particularly not into ha_partition.cc) so I think it would be good to wait for Oracle (or Percona, MariaDB, or Tokutek) to validate that it is correct before using it.

diff -u ha_partition.cc /tmp/ha_partition.cc 
--- ha_partition.cc 2013-04-05 05:27:18.000000000 -0700
+++ /tmp/ha_partition.cc 2013-05-27 02:45:01.680676228 -0700
@@ -6455,9 +6455,11 @@
void ha_partition::get_dynamic_partition_info(PARTITION_STATS *stat_info,
uint part_id)
{
+
handler *file= m_file[part_id];
DBUG_ASSERT(bitmap_is_set(&(m_part_info->read_partitions), part_id));
- file->info(HA_STATUS_CONST | HA_STATUS_TIME | HA_STATUS_VARIABLE |
+ 
+ info(HA_STATUS_CONST | HA_STATUS_TIME | HA_STATUS_VARIABLE |
HA_STATUS_VARIABLE_EXTRA | HA_STATUS_NO_LOCK);
stat_info->records= …

Recently I happen to setup a new MySQL instance with my tools – a standard MySQL 5.1+, xtrabackup setup and last-hotbackup.tar.gz. To restore from the backup we used xtrabackup binaries…

The post xtrabackup_51: not found & no ‘mysqld’ group in MySQL options first appeared on Change Is Inevitable.

I recently wrote about non-deterministic queries in the replication stream. That’s resolved by using either MIXED or ROW based replication rather than STATEMENT based.

Another thing that’s not fully handled by STATEMENT based replication is temporary tables. Imagine the following:

1. Master: CREATE TEMPORARY TABLE rpltmpbreak (i INT);
2. Wait for slave to replicate this statement, then stop and start mysqld (not just STOP/START SLAVE)
3. Master: INSERT INTO rpltmpbreak VALUES (1);
4. Slave: SHOW SLAVE STATUS \G

If for any reason a slave server shuts down and restarts after the temp table creation, replication will break because the temporary table will no longer exist on the restarted slave server. It’s obvious when you think about it, but nevertheless it’s quite …

Scaling up a workload to many cores on a single host

Here are results for Shard-Query 2.0 Beta 1* on the Star Schema Benchmark at scale factor 10.  In the comparison below the “single threaded” response times for InnoDB are the response times reported in my previous test which did not use Shard-Query.

Shard-Query configuration

Shard-Query has been configured to use a single host.  The Shard-Query configuration repository is stored on the host.  Gearman is also running on the host, as are the Gearman workers.  In short, only one host is involved in the testing.

The …

As you probably know, Tungsten Replicator can replicate data from MySQL to MongoDB. The installation is relatively simple and, once done, replication works very well. There was a bug in the installation procedure recently, and as I was testing that the breakage has been fixed, I wanted to share the experience of getting started with this replication.

Step 1: install a MySQL server

For this exercise, we will use a MySQL sandbox running MySQL 5.5.31.

We download the binaries from dev.mysql.com and install a sandbox, making sure that it is configured as master, and that it is used row-based-replication.

$ mkdir -p $HOME/opt/mysql
$ cd ~/downloads
$ wget …